Where to buy duct insulation wrap?

I have round metal air ducts that were leaking air. So I stripped off the old insulation, cleaned them out and sealed them with mastic. Where can I buy bulk insulation for air ducts. I plan to use the old fiberglass and foil combo.

To the OP, you didn't mention your location, but where I am (and it isn't a major city, by any means) I am able to find 15 insulation contractors in my immediate area that install and sell insulation products simply by using a hard copy of the yellow pages.
I know for a fact that at least 4 of these companies sell insulation specifically for air ducts because I work with them regularly on commercial HVAC jobs.
These companies will sell to the public as long as you know what you need before you show up or call because they generally don't have time to educate their customers.

Good luck!

__________________"The physician can bury his mistakes, but the architect can only advise his clients to plant vines." -- Frank Lloyd Wright